(A) Field of the Invention
The present invention relates generally to a digital joystick interface circuit, and more particularly to a trigger detecting circuit for resetting the trigger signals of a game interface and, via a comparator, achieving a circuit for coordinate addressing.
(B) Description of the Prior Art
Generally, the coordinate addressing of game interfaces is controlled by joysticks. A conventional joystick is shown in FIG. 2. It includes a variable resistance 10 for connecting a middle point thereof to a game port of the game interface. By means of the time delay caused by the variable resistance 10, resistor R1, and capacitor C1, coordinate addressing is achieved. However, problems occur is that variable resistance 10 is subject to damage, and the capacitor C1 is easily affected by ambient temperatures and generates errors so that delay is not precise, and causing the coordinates to be displaced. In another conventional joystick, shown in FIG. 1, a plurality of analog switches 20 are connected to a series of resistors which replace variable resistance 10. Although switching of contacts may prevent damage to the resistances to a certain extent, there is the problem of error with the capacitor C1 working in conjunction with the resistances to constitute the time delay. This is because, while this arrangement would be more precise if the capacitor were in a vacuum, changes in temperature will cause the capacitor to generate errors easily. At the same time, in order to make smaller capacitors, it is necessary to provide a dielectric in the middle. Therefore, the precision of the delay will be affected more easily. Besides, in order to achieve higher precision, such analog switch joysticks are usually provided with more resistances, hence increasing the probability of error and cost, which is very unsatisfactory indeed.